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//===-- WebAssemblyWasmObjectWriter.cpp - WebAssembly Wasm Writer ---------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
///
/// \file
/// This file handles Wasm-specific object emission, converting LLVM's
/// internal fixups into the appropriate relocations.
///
//===----------------------------------------------------------------------===//
#include "MCTargetDesc/WebAssemblyFixupKinds.h"
#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
#include "llvm/BinaryFormat/Wasm.h"
#include "llvm/MC/MCAsmBackend.h"
#include "llvm/MC/MCFixup.h"
#include "llvm/MC/MCFixupKindInfo.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCSectionWasm.h"
#include "llvm/MC/MCSymbolWasm.h"
#include "llvm/MC/MCValue.h"
#include "llvm/MC/MCWasmObjectWriter.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/ErrorHandling.h"
using namespace llvm;
namespace {
class WebAssemblyWasmObjectWriter final : public MCWasmObjectTargetWriter {
public:
explicit WebAssemblyWasmObjectWriter(bool Is64Bit, bool IsEmscripten);
private:
unsigned getRelocType(const MCValue &Target, const MCFixup &Fixup,
const MCSectionWasm &FixupSection,
bool IsLocRel) const override;
};
} // end anonymous namespace
WebAssemblyWasmObjectWriter::WebAssemblyWasmObjectWriter(bool Is64Bit,
bool IsEmscripten)
: MCWasmObjectTargetWriter(Is64Bit, IsEmscripten) {}
static const MCSection *getTargetSection(const MCExpr *Expr) {
if (auto SyExp = dyn_cast<MCSymbolRefExpr>(Expr)) {
if (SyExp->getSymbol().isInSection())
return &SyExp->getSymbol().getSection();
return nullptr;
}
if (auto BinOp = dyn_cast<MCBinaryExpr>(Expr)) {
auto SectionLHS = getTargetSection(BinOp->getLHS());
auto SectionRHS = getTargetSection(BinOp->getRHS());
return SectionLHS == SectionRHS ? nullptr : SectionLHS;
}
if (auto UnOp = dyn_cast<MCUnaryExpr>(Expr))
return getTargetSection(UnOp->getSubExpr());
return nullptr;
}
unsigned WebAssemblyWasmObjectWriter::getRelocType(
const MCValue &Target, const MCFixup &Fixup,
const MCSectionWasm &FixupSection, bool IsLocRel) const {
const MCSymbolRefExpr *RefA = Target.getSymA();
assert(RefA);
auto& SymA = cast<MCSymbolWasm>(RefA->getSymbol());
MCSymbolRefExpr::VariantKind Modifier = Target.getAccessVariant();
switch (Modifier) {
case MCSymbolRefExpr::VK_GOT:
case MCSymbolRefExpr::VK_WASM_GOT_TLS:
return wasm::R_WASM_GLOBAL_INDEX_LEB;
case MCSymbolRefExpr::VK_WASM_TBREL:
assert(SymA.isFunction());
return is64Bit() ? wasm::R_WASM_TABLE_INDEX_REL_SLEB64
: wasm::R_WASM_TABLE_INDEX_REL_SLEB;
case MCSymbolRefExpr::VK_WASM_TLSREL:
return is64Bit() ? wasm::R_WASM_MEMORY_ADDR_TLS_SLEB64
: wasm::R_WASM_MEMORY_ADDR_TLS_SLEB;
case MCSymbolRefExpr::VK_WASM_MBREL:
assert(SymA.isData());
return is64Bit() ? wasm::R_WASM_MEMORY_ADDR_REL_SLEB64
: wasm::R_WASM_MEMORY_ADDR_REL_SLEB;
case MCSymbolRefExpr::VK_WASM_TYPEINDEX:
return wasm::R_WASM_TYPE_INDEX_LEB;
case MCSymbolRefExpr::VK_None:
break;
default:
report_fatal_error("unknown VariantKind");
break;
}
switch (unsigned(Fixup.getKind())) {
case WebAssembly::fixup_sleb128_i32:
if (SymA.isFunction())
return wasm::R_WASM_TABLE_INDEX_SLEB;
return wasm::R_WASM_MEMORY_ADDR_SLEB;
case WebAssembly::fixup_sleb128_i64:
if (SymA.isFunction())
return wasm::R_WASM_TABLE_INDEX_SLEB64;
return wasm::R_WASM_MEMORY_ADDR_SLEB64;
case WebAssembly::fixup_uleb128_i32:
if (SymA.isGlobal())
return wasm::R_WASM_GLOBAL_INDEX_LEB;
if (SymA.isFunction())
return wasm::R_WASM_FUNCTION_INDEX_LEB;
if (SymA.isTag())
return wasm::R_WASM_TAG_INDEX_LEB;
if (SymA.isTable())
return wasm::R_WASM_TABLE_NUMBER_LEB;
return wasm::R_WASM_MEMORY_ADDR_LEB;
case WebAssembly::fixup_uleb128_i64:
assert(SymA.isData());
return wasm::R_WASM_MEMORY_ADDR_LEB64;
case FK_Data_4:
if (SymA.isFunction()) {
if (FixupSection.getKind().isMetadata())
return wasm::R_WASM_FUNCTION_OFFSET_I32;
assert(FixupSection.isWasmData());
return wasm::R_WASM_TABLE_INDEX_I32;
}
if (SymA.isGlobal())
return wasm::R_WASM_GLOBAL_INDEX_I32;
if (auto Section = static_cast<const MCSectionWasm *>(
getTargetSection(Fixup.getValue()))) {
if (Section->getKind().isText())
return wasm::R_WASM_FUNCTION_OFFSET_I32;
else if (!Section->isWasmData())
return wasm::R_WASM_SECTION_OFFSET_I32;
}
return IsLocRel ? wasm::R_WASM_MEMORY_ADDR_LOCREL_I32
: wasm::R_WASM_MEMORY_ADDR_I32;
case FK_Data_8:
if (SymA.isFunction()) {
if (FixupSection.getKind().isMetadata())
return wasm::R_WASM_FUNCTION_OFFSET_I64;
return wasm::R_WASM_TABLE_INDEX_I64;
}
if (SymA.isGlobal())
llvm_unreachable("unimplemented R_WASM_GLOBAL_INDEX_I64");
if (auto Section = static_cast<const MCSectionWasm *>(
getTargetSection(Fixup.getValue()))) {
if (Section->getKind().isText())
return wasm::R_WASM_FUNCTION_OFFSET_I64;
else if (!Section->isWasmData())
llvm_unreachable("unimplemented R_WASM_SECTION_OFFSET_I64");
}
assert(SymA.isData());
return wasm::R_WASM_MEMORY_ADDR_I64;
default:
llvm_unreachable("unimplemented fixup kind");
}
}
std::unique_ptr<MCObjectTargetWriter>
llvm::createWebAssemblyWasmObjectWriter(bool Is64Bit, bool IsEmscripten) {
return std::make_unique<WebAssemblyWasmObjectWriter>(Is64Bit, IsEmscripten);
}
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